Category: Powershell

Richie Lee has a method for checking whether a variable exists in Powershell:

Recently I needed to check that a variable exists in the PowerShell session currently running. This is actually far easier than it sounds. So here is a simple demo for how it works. The magic here is the “Test-Path variable:my_variable” on lines 4. It tests that a variable of that name exists. If it does, great, let’s print out the value. If not, let’s alert that it doesn’t. The second example of this on line 11 will do exactly that.

Read on to see Test-Path in action.

Amy Herold has a quick Powershell script to retrieve detailed system info (via msinfo32.exe) for a set of servers:

With this script you can generate system information files and save them to a specified location. It makes sure a connection can be made to the server first, and then outputs the file. The files are created one at a time, so if you pass in a longer list of servers, you shouldn’t crash your machine. From my testing, this will take some time to run as these files don’t output quickly. Despite that, the output is worth it. This can be modified to pull your list of servers from a file or from a Central Management Server (CMS) instance.

This is a useful script, with the next step being to turn it into a cmdlet that accepts the set of servers from the pipeline.

Jana Sattainathan has some thoughts on when to use each of the Write- cmdlets in Powershell:

PowerShell has matured as the automation tool of choice on the Microsoft platform, be it on Windows or Azure. However, there is no official guidance on best-practices and standards around some things. At times, bloggers do things incorrectly in their examples thereby reinforcing bad practices. Hopefully, this small post will help connect some dots for you! Please comment if I am stating something that is not a generally accepted best practice. Specifically, we are going to glance at the following cmdlets

• Write-Host

• Write-Output

• Write-Debug

• Write-Warning

• Write-Error/Throw

• Write-Verbose

• Write-Progress

Write-Host is the easiest and probably most controversial of the set (because its messages are outside the pipeline), but there’s a place for each of these.

Shane O’Neill shows the trick to excluding properties in Powershell:

Hmm, Properties, ExecutionManager, and URN (hidden from view) are not needed. That is not a problem, I’ll just pipe them to Select-Object and include them in the -ExcludeProperty parameter.

It’s not quite as straightforward as you’d imagine, but Shane shows you how to do it.

Rob Sewell shows how to make one parameter’s valid set of values depend upon a previous parameter’s selected value:

But what Sander wanted was to validate the value of the second parameter depending on the value of the first one. So lets say we wanted

• If word is sun, number must be 1 or 2
• If word is moon, number must be 3 or 4
• If word is earth, number must be 5 or 6

We can use the ValidateScriptAttribute  to do this. This requires a script block which returns True or False. You can access the current parameter with $_ so we can use a script block like this

Any Powershell post with a link to June Blender is automatically 5% better in my book.